The present invention relates to an ultrasound probe and a method for connecting signal lines, in particular, to an ultrasound probe having a plurality of signal lines which are drawn out from a plurality of piezoelectric elements and are connected to an ultrasound diagnostic apparatus body through communication cables and a method for connecting the signal lines.
Conventionally, ultrasound diagnostic apparatuses using ultrasound images have been put to practical use in the medical field. In general, an ultrasound diagnostic apparatus of this type transmits an ultrasonic beam from a plurality of piezoelectric elements of an ultrasound probe into a subject's body, receives the echo from the subject with the plurality of piezoelectric elements of the ultrasound probe, and electrically processes the resulting reception signals in an ultrasound diagnostic apparatus body to produce an ultrasound image.
Recently, in order to improve ultrasound image resolution, ultrasound probes that transmit and receive high-frequency ultrasonic beams have come into practical use. Through transmission and reception of high-frequency ultrasonic beams, ultrasonic echoes from objects that are present at short distances within a subject's body can be individually obtained, whereby the resolution can be improved. On the other hand, there has been a problem that use of a high-frequency ultrasonic beam in ultrasound diagnosis would easily invite noise mixture. For example, as signals have the higher frequency, reception signals respectively received by the plurality of piezoelectric elements of the ultrasound probe are likely to cause electric cross-talk among them. As a result, the signal-to-noise ratio of reception signals significantly drops. In addition, a high-frequency ultrasonic beam readily attenuates as propagating within the subject's body, which will be another cause of a decrease in the signal-to-noise ratio.
In order to suppress the decrease in the signal-to-noise ratio of reception signals, the plurality of reception signals received by the plurality of piezoelectric elements of the ultrasound probe are transmitted to the ultrasound diagnostic apparatus body through coaxial cables, respectively. In this manner, reception signals can be kept from being affected by electric cross-talk or the like, and the decrease in the signal-to-noise ratio of reception signals can be suppressed. On the other hand, it is difficult to thoroughly connect from the plurality of piezoelectric elements of the ultrasound probe to the ultrasound diagnostic apparatus body with coaxial cables. For example, drawn-out signal lines that are drawn out from signal electrodes of the plurality of piezoelectric elements to the outside are connected to the coaxial cables via connection conductors formed on a printed board. Since the drawn-out signal lines and the connection conductors are not shielded from each other, noises would be possibly mixed in reception signals transmitting therebetween.
Accordingly, as a technology for suppressing noise mixture into reception signals, there has been proposed provision of grounded conductive layers each being disposed between adjacent connection conductors formed on a printed board as disclosed, for example, in JP 06-105396 A.
In the ultrasound probe described in JP 06-105396 A, the respective grounded conductive layers suppress cross-talk among connection conductors and can thus suppress noise mixture into reception signals.
However, it is difficult to drastically suppress an influence of cross-talk among connection conductors or an electric influence from the outside merely by means of provision of the grounded conductive layers each being disposed between adjacent connection conductors. In particular, when the ultrasonic echo received by the ultrasound probe has a center frequency of 10 MHz or higher, its electric influence would possibly be a major cause of a decrease in the signal-to-noise ratio of reception signals.